1. Field of the Invention
The present invention relates to a method of involute interpolation for a computerized numerical control apparatus having a rotational axis and a linear axis, and more particularly to a method of involute interpolation for interpolating an involute curve and a Z-axis in synchronism with each other.
2. Description of Related Art
There is a great need for the interpolation of involute curves in computerized numerical control apparatus or the like in order to machine gears, pump impellers, or the like. It has been general practice to interpolate an involute curve with a computer or an NC programming device separate from a numerical control apparatus, convert the interpolated data to linear data on a tape, and machine a workpiece under numerical control using the tape.
The applicant has proposed an involute interpolation method by which an involute curve can easily be interpolated with commands in an orthogonal coordinate system within a computerized numerical control (CNC) apparatus (see Japanese Patent Application No. 62-157303).
The machine coordinate system of a three-axis lathe or a cam grinding machine having a C-axis is a polar coordinate system. There, an involute interpolation method which employs an orthogonal coordinate system cannot be applied to these machines.
For machining a cam or a gear, it is necessary to interpolate an involute curve in one plane, and provide a curved plane which moves in a direction normal to that plane.